rst-lint on Doc/ folder too

Currently just Doc/doc.rst from the CodonAlign work.

Note I would like to run 'rst-lint --level warning .'
but currently that breaks due to the tools' own test
cases present under the .tox folder.

.travis-tox.ini

@@ -105,7 +105,7 @@ commands =
     flake8 Tests/
     # Now do various checks on our RST files:
     # Calling via bash to get it to expand the wildcard for us
-    bash -c \'rst-lint --level warning *.rst\'
+    bash -c \'rst-lint --level warning *.rst Doc\'
     # Check sort order (bash call work around for pipe character)
     bash -c \'grep "^- " CONTRIB.rst | LC_ALL=C sort -u -c -f\'
     # Check copyright date